The Great Snail Tug-O-War

(Download the MS Word version of this document.)

Purpose

To compare the strength of humans with that of snails.

Materials

• beaker of water
• celery
• triple-beam balance
• scale large enough to weigh humans
• large land snails
• dixie cup
• masking tape
• dental floss
• dufflebag and rope
• towel
• weights for humans and snails
• metric ruler
• spray bottle with water

Procedure

1. While the Technician is collecting your supplies, the Recorder should copy the lab title and purpose onto the group paper. Write in all team members' names and their abbreviated job titles. Place your team number in the upper left-hand corner of your paper and circle it. Below the purpose, write "PROBLEM" and then copy the following statement: "Which organism — a human or a snail — is able to pull more mass compared to its body mass?"
2. Write the word "HYPOTHESIS" below your problem question. Discuss in your group what you think the answer to the problem question will be. Write down the group's hypothesis here.
3. Your first task is to determine what kinds of things motivate snails. Place your snail on the table top. Use celery and water to assist you in making observations.
   1. List five observations about the behavior of the land snail.
4. Make certain your triple-beam balance is calibrated. Use the balance to record the mass in grams of the following:
   1. snail
   2. dixie cup with dental floss
   3. various metal weights
5. Now you are going to see how much mass the snail is able to pull. Tape the dental floss (attached to the dixie cup) to the top of the snail's shell. NOTE: Make certain the shell is dry before you try to attach the tape. Add a large weight to the dixie cup.
6. Place the snail in the center of your table and lay the ruler next to the cup. Use the celery or a small pool of water to entice the snail to move forward. If the snail is able to drag the weighted cup at least one centimeter, add more weight to the cup. In order to determine the maximum amount of mass the snail is able to pull, continue adding weights until the snail is no longer able to drag the cup. (Remember to subtract the last weight added from the total number of weights since the snail was unable to drag this.) The Technician should now remove the tape and return the snail to the teacher.
7. Title this section of your lab paper "DATA COLLECTION #1." Make a chart to record the total mass of the objects the snail was able to pull. Use the example below as a guide to making your chart.

   Mass of weights pulled + Mass of dixie cup with dental floss = Total Mass Pulled
   Snail's Mass =

   1. Total Mass Pulled is what percent of the Snail's Mass? [Show your work.]
8. Now predict how much mass your Maintenance Director can pull across the floor.
   1. Prediction of how much mass a human can pull across the floor =
9. Title this section of your lab paper "DATA COLLECTION #2." Your teacher will help test your maintenance director's pulling ability. Have the Maintenance Director wear the rope connected to the dufflebag around his or her waist. Add towels around the rope to prevent it cutting into the waist. Begin with 90 lb by placing two 45-lb weights inside the dufflebag. Add weights as needed until the Maintenance Director can no longer steadily drag the dufflebag. CAUTION: Advise the maintenance director to keep his/her back straight and knees bent! He or she must be able to pull the weights at least 1 meter. Lay the meter stick on the floor so you can see how far the weights have been pulled. Make a chart to record the mass that was pulled by the Maintenance Director. Use the following chart as a guide for your chart.

   Actual amount of mass pulled =
   Maintenance Director's mass

   1. What percentage of his/her body mass was pulled?
10. Title this section of your lab paper "CONCLUSIONS." [A two- or three-sentence conclusion will suffice as you will be summarizing this laboratory exercise later.]
11. Now your group should review how snails function in their day-to-day life activities. Each member of your team has been given a handout with a diagram of a snail. Using your textbook and the handout from Animals Without Backbones titled "Soft-Bodied Animals," each team member should label the parts of the snail on the handout. Then answer the following questions on your group lab paper.
    1. Which organisms are the most numerous of all the molluscs?
    2. What does the term "mollusc" mean?
    3. Describe how a snail feeds using its radula. [Hint: Snails feed in the same manner as chitons.]
    4. Snails have an open circulatory system. Explain how this is different from a closed circulatory system.
    5. Most molluscs have bilateral symmetry. What kind of symmetry do snails exhibit?
    6. What is the benefit to the snail of having this type of symmetry?
    7. Define the term "torsion."
    8. What are "pulmonates"? Give two examples of pulmonates.
12. On his or her own paper, each team member should write a one- to two-paragraph summary of this experiment. Be certain you include the following information: (1) purpose of the experiment, (2) major findings, (3) whether the hypothesis was supported by the data collected, (4) possible explanations for your findings, (5) recommendations for further study and/or for improving the experiment.